This invention relates to mammography methods and to apparatus for carrying out such methods.
Currently, on an international scale, ultrasound breast examination is an accepted medical modality applied both as a primary method for evaluation of the breasts of young patients, that is, those under 40 years of age, and as an adjunct to x-ray mammography. See, for example, Kasumi, F., et cl., xe2x80x9cTopics in Breast Ultrasound,xe2x80x9d Seventh International Congress on the Ultrasonic Examination of the Breast, Shinohara Publications, Inc., 1-7, Hongo 2-chome, Bunkyo-ku, Tokyo 113, Japan, 1991; Tohno E., et al., Ultrasound Diagnosis of Breast Diseases, New York, Churchill-Livingstone, 1994; and Stavros, A. T. et al., xe2x80x9cSolid Breast Nodules: Use of Sonography to Distinguish Between Benign and Malignant Lesions,xe2x80x9d Radiology 196, pp. 123-134, 1995. In terms of the diagnostic effectiveness of the ultrasound breast imaging, a number of investigators from the early 1980s to the present have shown that this modality is not limited to diagnosing the solid or cystic nature of a breast mass. It is capable, with a high degrees of accuracy, of providing imaging data which permits differentiation of benign and malignant breast masses. See, for example, Stavros, A. T., et al., xe2x80x9cSolid Breast Nodules: Use of Sonography to Distinguish Between Benign and Malignant Lesions,xe2x80x9d Radiology 196, pp. 123-134, 1995; Kelly-Fry, El, et al., xe2x80x9cFactors Critical to Highly Accurate Diagnosis of Malignant Breast Pathologies by Ultrasound Imaging,xe2x80x9d Ultrasound 82 eds., Lerski, R. A. et al., Pergamon Press, Oxford and New York, 1983; Harper, P., et al., xe2x80x9cBreast Ultrasound: Report of a 5-Year Combined Clinical and Research Program,xe2x80x9d Le Journal Francais d""Echograplaie, 2n 5, pp. 133-139, 1984; Ueno, E., et al., xe2x80x9cClassification and Diagnostic Criteria in Breast Echography,xe2x80x9d Japan Journal of Medicine, Ultrasonics, vol. 13, no. 1, pp. 19-31, 1986 (in English); Ueno E., et al., xe2x80x9cDynamic Tests in Real-Time Breast Echography,xe2x80x9d Ultrasound in Med. and Biology, 14 (supp. 1), pp. 53-57, 1988, Tohnosu, N., et al., xe2x80x9cClinical Evaluation of Ultrasound in Breast Cancers in Compression with Mammography, Computed Tonography and Digital Subtraction Angiography,xe2x80x9d Topics in Breast Ultrasound, eds., Kasume, F., et al., Shinohara Pub. Inc., Tokyo, Japan, 1991; and Gerlach, B., et al., xe2x80x9cComparison of X-ray Mammography and Sonomammography of 1,209 Histological Verified Breast Diseases,xe2x80x9d Breast Ultrasound Update, eds., Madjar, H., et al., Karger, Bascl, Freiburg, New York, 1994. In Japan, ultrasound breast imaging has equal diagnostic status with x-ray mammography. See, for example, Ueno, E., et al., xe2x80x9cDynamic Tests in Real-Time Breast Echography,xe2x80x9d Ultrasound in Med. and Biology, 14 (supp. 1), pp. 53-57, 1988; Tohnosu, N., et al., xe2x80x9cClinical Evaluation of Ultrasound in Breast Cancers in Compression with Mammography, Computed Tomography and Digital Subtractions Angiography,xe2x80x9d Topics in Breast Ultrasound, eds., Kasumi, F., et al., Shinohara Pub. Inc., Tokyo, Japan, 1991. European investigators have found that ultrasound breast imaging can equal the accuracy of x-ray mammography in the diagnosis of overt, malignant breast masses. See, for example, Gerlach, B., et al., xe2x80x9cComparison of X-ray Mammography and Sonomammography of 1,209 Histological Verified Breast Diseases,xe2x80x9d Breast Ultrasound Update, eds., Madjar, H., et al., Karger, Basel, Freiburg, New York, 1994; Dambrosio, F., et al., xe2x80x9cClinical Program of Breast Surveillance by Means of Echopalpation; Results from January 1985 to May 1992,xe2x80x9d Breast Ultrasound Update, eds., Madjar, H. et al., Karger, Basel, Freiburg, New York, 1994; and, Leucht, W., et al., xe2x80x9cIs Breast Sonography an Additional Method for the Diagnosis of Palpable Masses,xe2x80x9d Topics in Breast Ultrasound, eds., Kasumi, F., et al., Shinohara Pub. Inc., 11-7 Hongo 2-chome, Bunkyo-ku, Tokyo 113, Japan, 1991. In the United States, many clinicians during the 1980s and early 1990s restricted ultrasound breast imaging to a limited role of differentiation between cystic and solid masses. See, for example, Sickles, E. A., xe2x80x9cImaging Techniques Other Than Mammography for the Detection and Diagnosis of Breast Cancer,xe2x80x9d Recent Results in Cancer Research, 119, pp. 127-135, 1990; Jackson, V. P., xe2x80x9cThe Role of US in Breast Imaging,xe2x80x9d Radiology, 117, pp. 305-311, 1990; Bassett, L. W. et al., xe2x80x9cBreast Sonography,xe2x80x9d American Journal of Radiology, 156 (3), pp. 449-455, 1991; Feig, S. A., xe2x80x9cBreast Masses: Mammographic and Sonographic Evaluation,xe2x80x9d Radiol. Clin. North Am., 30, pp. 67-93, 1992; and Orel, S. G., et al., xe2x80x9cNonmammographic Imaging of the Breast: Current Issues and Future Prospects,xe2x80x9d Sem. In Roentgenology, XXVIII, no. 3, pp. 231-241, 1993. Following the 1995 publication of a clinical study which provided further data on the successful differentiation of benign and malignant masses by ultrasound breast imaging techniques, this modality was more widely applied in the United States. See, for example, Stavros, A. T. et al., xe2x80x9cSolid Breast Nodules: Use of Sonography to Distinguish Between Benign and Malignant Lesions,xe2x80x9d Radiology 196, pp. 123-134, 1995.
Since the 1980s, most ultrasound breast examinations have been carried out with the patient in the supine position. Imaging is carried out by moving a hand-held ultrasound transducer across the free flowing surface of the breast and recording the images on film. By contrast, for x-ray mammography, the patient is in a standing or sitting position with the breast compressed between a plastic paddle and the surface of an x-ray film holder module. The breast is alternately compressed in various orientations such as cranio-caudal, lateral and oblique while the x-ray beam traverses the breast in each of these positions. For each individual position, an image is recorded. Currently, to correlate precisely standard breast ultrasound imaging data with that provided by x-ray mammography data can sometimes be impossible because the anatomical orientations of tissues traversed by the x-ray beam for the various compressed breast positions are different from the anatomical position of tissues traversed by the ultrasound beam following its entrance into an uncompressed breast in a supine position. Also, since tissue is mobile, the location of a breast mass as imaged when a breast is compressed between two plates can be different from that of its imaged location when the breast is uncompressed and in a supine position. These problems can lead to diagnostic errors.
In an attempt to improve correlation between ultrasound and x-ray imaging data, in 1983 Novak demonstrated a technique for holding the breast in the same positions used in x-ray mammography while applying a linear array ultrasound transducer in direct contact with the breast surface. See, Novak, D., xe2x80x9cIndications for and Comparative Diagnostic Value of Combined Ultrasound and X-ray Mammography,xe2x80x9d European Journal of Radiology, 3, 1983. A plexiglas plate was used as a support on one side of the breast while the ultrasound transducer contacted the skin surface of the opposite side. The breast was not compressed between two plates.
In the early 1990s, Kelly-Fry, et al, demonstrated that specially designed breast compression paddles, constructed from various types and thicknesses of plastics, including polyesters, polycarbonates and acrylics, can transfer both x-ray and ultrasound, without serious attenuation of either modality. See, for example: Kelly-Fry, E., et al, xe2x80x9cA New Ultrasound Mammography Technique That Provides Improved Correlation With X-ray Mammography,xe2x80x9d Amer. Col. Radiol., 24th National Conference on Breast Cancer, New Orleans, La., March 1990, Kelly-Fry, E., et al, xe2x80x9cAdaptation, Development and Expansion of X-ray Mammography Techniques for Ultrasound Mammography,xe2x80x9d Journal of Ultrasound in Medicine, 10, no. 3, S 16, supplement, March 1991; Kelly-Fry, E., xe2x80x9cNew Techniques for Ultrasound Mammography,xe2x80x9d National Cancer Institute Breast Imaging Workshop, Bethesda, Md., Sep. 4-6, 1991; and, Kelly-Fry, E., et al, xe2x80x9cRapid Ultrasound Scanning of Both Breasts Positioned and Compressed in the Mode of X-ray Mammography,xe2x80x9d Journal of Ultrasound in Medicine, 13, no. 3, S41-42 supplement, March, 1994. Instrumentation systems which incorporated these compression paddles were designed and applied to patients with the purpose of ultrasonically imaging a breast while it was held under the same compression and position orientations used in x-ray mammography. A hand-held ultrasound linear array transducer placed in contact with the compression plate was used for imaging.
Subsequent investigations of this approach by Dines, et al, Romilly-Harper, et al, and Kelly-Fry, et al, included automation of the transducer motion, use of high ultrasound frequencies, such as, for example, 7.5 MHZ, 10 MHZ and 13 MHZ, 3D ultrasound imaging and clinical application of the system. See, for example, Dines, K. A., et al, xe2x80x9cAutomated Three-Dimensional Ultrasound Breast Scanning in the Craniocaudal Mammography Position,xe2x80x9d Ninth International Congress on the Ultrasonic Examination of the Breast, Sep. 28-Oct. 1, 1995, pp. 43-44; Dines, K. A., et al, xe2x80x9cAutomated Three-Dimensional Ultrasonic Breast Scanning in the Compressed Mammography Position,xe2x80x9d Journal of Ultrasound in Medicine, vol. 18, no. 3, supplement, March, 1999; Romilly-Harper, A. P., et al, xe2x80x9cClinical Evaluation of Manual, Automated and 3-D Ultrasound Imaging of Breasts Compressed in the Same Position Modes Applied in X-ray Mammography,xe2x80x9d Ninth International Congress on the Ultrasonic Examination of the Breast, Sep. 28-Oct. 1, 1995, pp. 45-46; and, Kelly-Fry, E., et al, xe2x80x9cMammography Instrumentation for Combined X-ray and Ultrasound Imaging,xe2x80x9d Ninth International Congress on the Ultrasonic Examination of the Breast, Sep. 28-Oct. 1, 1995.
To obtain data on the ultrasound attenuation and velocity of breast tumors, Richter designed a system in which a breast is compressed between two thick, for example, approximately 0.39 inch (10 mm), plexiglas plates, in the craniocaudal position. A metal reflector is placed on the inferior plexiglas plate and a linear array transducer is in contact with the upper plate. See, for example, Richter, K., xe2x80x9cTechnique for Detecting and Evaluating Breast Lesions,xe2x80x9d Journal of Ultrasound in Medicine, 13, pp. 797-802, 1994 and Richter, K. xe2x80x9cDetection of Diffuse Breast Cancers with a New Sonographic Method,xe2x80x9d J. Clin. Ultrasound, 24, pp. 157-168, May, 1996. No x-ray imaging system was included in this initial instrumentation. The thick plexiglas compression paddle was inappropriate for x-ray breast imaging because of its increased attenuation of the x-ray beam. See, for example, Kelly-Fry, E., et al, xe2x80x9cMammography Instrumentation for Combined X-ray and Ultrasound Imaging,xe2x80x9d Ninth International Congress on the Ultrasonic Examination of the Breast, Sep. 28-Oct. 1, 1995. The thickness of the compression plate was also inappropriate for ultrasound imaging, causing increased ultrasound attenuation and multiple artifactual reflections within the breast image. In subsequent investigations, Richter, et al, carried out clinical studies at a low frequency, 5 MHZ, using automated transducer motion with attachment of the imaging system to a standard x-ray unit. See, for example, Richter, et al, xe2x80x9cDescription and First Clinical Use of a New System for Combined Mammography and Automated Clinical Amplitude/Velocity Reconstructive Imaging (CARI) Breast Sonography, Invest. Radiol.xe2x80x9d 32, pp. 19-28, 1997, Richter, K., et al, xe2x80x9cDetection of Malignant and Benign Breast Lesions with an Automated US System: Results in 120 Cases,xe2x80x9d Radiology, 205, pp. 823-830, 1997; U.S. Pat. Nos. 5,603,326; and, 5,840,022.
Other patents illustrate and describe instrument systems which combine x-ray mammography and ultrasound mammography using breast compression materials that are radiolucent and sonolucent. See, for example, U.S. Pat. Nos. 5,474,072, 5,479,927; and WO 95/11627. Earlier publications on the development and application of a combined x-ray and ultrasound mammography system using breast compression paddles that transmit both x-rays and ultrasound are not referenced. A breast examination system based upon these references was commercially marketed as a 3D ultrasound-guided breast biopsy system.
U.S. Pat. No. 5,776,062 illustrates and describes a system for applying x-rays to identify a region in a breast containing a possible malignant mass. Subsequently, ultrasound imaging is performed in order to target the x-ray identified region. Ultrasound-guided biopsy is then based on the combined data. The system is not designed for ultrasound scanning of the whole breast. Ultrasound imaging takes place via an opening in a substitute breast compression paddle, rather than via application of an ultrasound transducer in direct contact with the breast compression paddle used for the x-ray imaging. Interruption between the x-ray and ultrasound imaging procedures is required for this procedure.
With respect to 3-D ultrasound imaging, Itoh, et al, developed an early ultrasound instrumentation system which provided just the outlines, that is, the shape, in three dimensions, of a breast mass. See, for example, Itoh, et al, xe2x80x9cA Computer-Aided Three-Dimensional Display System for Ultrasonic Diagnosis of a Breast Tumor,xe2x80x9d Ultrasonics, pp. 261-268, November, 1979. The 3-D images only included breast tumor contour outlines obtained by digitizing and computer processing image data from standard B-mode volume scans.
In 1982, J. F. Greenleaf carried out investigations of 3-D ultrasound imaging of excised breasts by digitizing and computer processing standard B-mode image data. See Greenleaf, J. F., xe2x80x9cThree-Dimensional Imaging in Ultrasound,xe2x80x9d J. of Med. Systems, vol. 6, no. 6, pp. 580-589, 1982.
Rotten, et al, performed 3-D breast imaging using direct contact of a standard ultrasound transducer on the uncompressed breasts of subjects lying in supine position. See, for example, Rotten, D., et al, xe2x80x9cThree Dimensional Imaging of Solid Breast Tumors With Ultrasound: Preliminary Data and Analysis of Its Possible Contribution to the Understanding of the Standard Two-Dimensional Sonographic Images,xe2x80x9d Ultrasound Obstet. Gynecol., vol. 1, pp. 384-390, 1991, and Rotten, D., et al, xe2x80x9cAnalysis of Normal Breast Tissue and of Solid Breast Masses Using Three-Dimensional Ultrasound Mammography,xe2x80x9d Ultrasound Obstet. Gynecol., vol. 14, 114-124, 1999. This image data was processed by a graphic work station with three-dimensional software. The system was not designed for a precise comparison between ultrasound images and x-ray images in terms of ultrasonically imaging a breast while it is held in the same positions and under the same compression for each modality.
Hernandez, et al, in an investigation of stereoscopic visualization of 3D ultrasound breast images used a plexiglas plate to compress a breast in a craniocaudal position. A linear phased array transducer was automatically translated across the compressed breast. The ultrasound imaging was not performed by directing the ultrasound through the plexiglas, but rather, by directing the ultrasound through an opening in the plexiglas. See Hernandez, A., et al, xe2x80x9cStereoscopic Visualization of Three-Dimensional Ultrasonic Data Applied to Breast Tumors,xe2x80x9d Eur. J. Ultrasound, vol. 8, no. 1, pp. 51-65, September 1998.
Various other apparatus and methods for conducting mammography are known. There are, for example, the methods and apparatus described in the following listed references: U.S. Pat. Nos. 5,640,956; 5,664,573; 5,938,613; Kelly-Fry, E., et al, xe2x80x9cThe Rationale For Ultrasound Imaging of Breasts Compressed and Positioned in the Modes Applied in X-ray Mammography,xe2x80x9d International Breast Ultrasound School, Sep. 28-Oct. 1, 1995, pp. 126-129. This background is not intended as a representation that a thorough search of the prior art has been conducted or that no more pertinent art than that listed above exists, and no such representation should be inferred.
Though x-ray mammography is a well-accepted imaging modality for breast cancer detection, it has several shortcomings. First of all, only a through-transmission image related to integrated tissue density is obtained. Overlying diagnostic features are summed together, resulting in the possibility that important information is blurred, summed, and overlaid so it cannot be detected in the x-ray image. A further shortcoming is that the breast is imaged only up to the chest wall, but there may be abnormalities further in that are not recorded on the x-ray film. The present invention provides an additional imaging view particularly appropriate for this latter situation.
According to one aspect of the invention, a system for generating a three-dimensional image of the compressed breast of a subject includes an x-ray mammography unit for generating x-ray mammography data, a mechanical scanner including an x-ray mammography compression paddle assembly, a control and motion system for driving the mechanical scanner and for sensing the control and motion system""s position, an ultrasound probe for generating ultrasound image data in spatial registration with the x-ray mammography unit, and a computer for generating from the ultrasound image data and the x-ray mammography data the three-dimensional ultrasound image.
Illustratively according to this aspect of the invention, the ultrasound probe is a linear array probe.
Further illustratively according to this aspect of the invention, the apparatus includes a display for displaying the three-dimensional images.
Additionally illustratively according to this aspect of the invention, the apparatus includes a display for displaying two-dimensional ultrasound images.
Illustratively according to this aspect of the invention, the two-dimensional ultrasound images include B-mode images and the display for displaying two-dimensional ultrasound images is a display for displaying B-mode images.
Additionally illustratively according to this aspect of the invention, the apparatus includes an image capture device for capturing the B-mode images.
Illustratively according to this aspect of the invention, the x-ray mammography unit includes a vertical x-ray support column with a movable arm. The arm supports an x-ray tube. The x-ray mammography unit further includes a movable paddle mount block, a detector assembly including an x-ray image detector, and a lower compression surface for supporting the underside of compressed breast.
Further illustratively according to this aspect of the invention, the mechanical scanner is connected to the compression paddle assembly. The compression paddle assembly is connected to the paddle mount block. Force applied by the paddle mount block compresses the breast under the compression paddle assembly.
Additionally illustratively according to this aspect of the invention, the movable arm can be rotated in a plane parallel to the patient""s chest wall and positioned vertically so that the patient""s breast can be inserted between the compression paddle assembly and the lower compression plate over a range of angular rotations of the movable arm.
Illustratively according to this aspect of the invention, the paddle mount block is mounted so as to permit it to be translated far enough to provide enough room for the patient""s breast to fit between the compression paddle assembly and the detector assembly, for both the cranio-caudal and lateral-oblique positions. Further, such translation is designed to permit the patient""s body to fit between the compression paddle assembly and the detector assembly for imaging in the head-on position.
Further illustratively according to this aspect of the invention, the motion system includes a three-dimensional mechanical positioning system for scanning ultrasound probe across breast under control of the computer to yield a three-dimensional image registered to a spatial coordinate frame.
Additionally illustratively according to this aspect of the invention, the mechanical scanner includes at least one X-axis actuator, at least one Y-axis actuator, and a Z-axis positioner. Illustratively, the at least one Y-axis actuator includes a left Y-axis actuator and a right Y-axis actuator. Further illustratively, the left Y-axis actuator and the right Y-axis actuator are attached in parallel to a support bar.
Illustratively according to this aspect of the invention, the X-axis actuator is mounted across the Y-axis actuators for positioning the Z-axis positioner carrying the ultrasound probe.
Further illustratively according to this aspect of the invention, the compression paddle assembly is fitted between the Y-axis actuators.
Additionally illustratively according to this aspect of the invention, the compression paddle assembly includes an ultrasound imaging compression paddle constructed from plastic. Illustratively, the plastic is a polycarbonate plastic.
Further illustratively according to this aspect of the invention, the apparatus includes a Z-axis position encoder for providing an input to the computer for use in three-dimensional image construction.
Illustratively according to this aspect of the invention, the Z-axis position encoder includes an encoder linkage, a linear encoder sensor, and a linear encoder graticule for monitoring the Z-position of the ultrasound probe.
According to another aspect of the invention, a method of examining a breast of a subject includes contacting an anterior surface of the breast with a compression paddle, applying pressure to the anterior surface of the breast with the compression paddle to compress it to reduce the thickness of the breast tissue between the compression paddle and the anterior wall of the subject""s chest, passing an ultrasound beam having a frequency of greater than 3 MHz, perferrably about 5 MHZ or more, through the paddle and the compressed breast tissue, receiving echoes from the compressed breast tissue through the compression paddle, and converting the echoes into breast examination data.
Illustratively according to this aspect of the invention, contacting an anterior surface of the breast of the subject includes contacting an anterior surface of the breast of a standing subject.
Alternatively illustratively according to this aspect of the invention, contacting an anterior surface of the breast of the subject includes contacting an anterior surface of the breast of a sitting subject.
Further illustratively according to this aspect of the invention, contacting an anterior surface of the breast with a compression paddle includes contacting an anterior surface of the breast with a compression paddle constructed from plastic.
Additionally illustratively according to this aspect of the invention, contacting an anterior surface of the breast with a compression paddle constructed from plastic includes contacting an anterior surface of the breast with a compression paddle constructed from a polycarbonate plastic.
Illustratively according to this aspect of the invention, contacting an anterior surface of the breast with a compression paddle includes contacting an anterior surface of the breast with a compression paddle having a thickness not greater than about 0.12 inch (about 3 mm).
Further illustratively according to this aspect of the invention, applying pressure to the anterior surface of the breast with the compression paddle to compress it includes applying pressure to the anterior surface of the breast with the compression paddle under motor control.
Additionally illustratively according to this aspect of the invention, passing an ultrasound beam having a frequency greater than 3 MHz, perferrably about 5 MHZ or more, through the paddle and the compressed breast tissue includes passing an ultrasound beam having a frequency greater than 3 MHz, perferrably about 5 MHZ or more, generated by a linear array ultrasound transducer through the paddle and the compressed breast tissue in direct contact with the paddle.
Illustratively according to this aspect of the invention, passing an ultrasound beam having a frequency greater than 3 MHz, perferrably about 5 MHZ or more, MHZ through the paddle and the compressed breast tissue includes scanning an ultrasound transducer across a surface of the paddle opposite the surface of the paddle in contact with the compressed breast.
Further illustratively according to this aspect of the invention, scanning an ultrasound transducer across a surface of the paddle includes manually scanning an ultrasound transducer across a surface of the paddle.
Alternatively illustratively according to this aspect of the invention, scanning an ultrasound transducer across a surface of the paddle includes automatically scanning an ultrasound transducer across a surface of the paddle.